Failure to find behavioural differences between lean and obese Zucker rats exposed to novel environments.

Past studies have evidenced a key role for hypercorticism in the obesity syndrome of the Zucker (fa/fa) rat. Here, the hypothesis that obesity-related hypercorticism is associated with increased anxiety/emotionality was tested in the elevated plus-maze, the black/white box, and the open field. In the elevated plus-maze, none of the parameters examined (open arm entries, time in open arms, total number of entries) differed between lean (Fa/?) and obese (fa/fa) rats. In addition, neither the behaviours measured in the black/white box (latency to enter the black compartment, number of transitions, time spent in the white compartment, locomotion, rearing) nor those measured in the open field (locomotion, rearing, grooming, defecation) were affected by obesity. This study suggests that obesity-related hypercorticism in fa/fa rats is not associated with indices of emotionality and anxiety, at least those analysed by means of the tests used here.